LTC2500-32 ENOB

Hi ADI Expert, 

According to the datasheet page8 of LTC2500-32 Performance characteristics,

SNR: 116dB, SINAD:114dB @ 128K FFT, SSINC filter. thus I calculated the ENOB= SINAD 114dB -1.76dB/6.02 = 18.6 Bits.

The datasheet page32 table2 is noise performance at digital filter.

SSINC DF=4, noise is 6.97 uVrms

Thus I calculated the ENOB as blow.

ENOB=log2 (Fullscale 5Vx2 / 6.19uVrms)= 20.6 bits

Those ENOB performance has 2 bits gap between 18.6 and 20.6 bits, Is any thing wrong for my calculating?

The next question is if I used the best noise performance 0.15uVrms at SSINC filter DF 16384

Log2( FullScale 10V/0.15uV) = 25.99 ENOB

Noise-free resolution = Log2 (10V/0.15uVx6.6) = 23.2 Bits.

So this is the best performance for LT2500-32 32bit ADC, Am I right?

Best Regards.


[edited by: RayW at 2:55 AM (GMT 0) on 26 May 2020]
    •  Analog Employees 
    on May 26, 2020 2:27 PM 6 months ago

    In calculating ENOB, SINAD is more often used than SNR. Also the full scale value used should be in RMS which are the units used for the noise. RMS full scale for a 10Vpp signal is 3.54V. At some point the ENOB performance will limited by the THD of the LTC2500-32.